diff --git a/.github/workflows/depup.yml b/.github/workflows/depup.yml
index 226aeef..992bc86 100644
--- a/.github/workflows/depup.yml
+++ b/.github/workflows/depup.yml
@@ -10,7 +10,7 @@ jobs:
   reviewdog:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: reviewdog/action-depup@v1
         id: depup
         with:
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 68b0f3d..2d7e8e4 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -14,7 +14,7 @@ jobs:
     if: github.event.action != 'labeled'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
 
       # Bump version on merging Pull Requests with specific labels.
       # (bump:major,bump:minor,bump:patch)
@@ -52,6 +52,6 @@ jobs:
     if: github.event.action == 'labeled'
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - name: Post bumpr status comment
         uses: haya14busa/action-bumpr@v1
diff --git a/.github/workflows/reviewdog.yml b/.github/workflows/reviewdog.yml
index d4941ec..0239884 100644
--- a/.github/workflows/reviewdog.yml
+++ b/.github/workflows/reviewdog.yml
@@ -9,7 +9,7 @@ jobs:
     name: runner / shellcheck
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: haya14busa/action-cond@v1
         id: reporter
         with:
@@ -26,7 +26,7 @@ jobs:
     name: runner / misspell
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: reviewdog/action-misspell@v1
         with:
           github_token: ${{ secrets.github_token }}
@@ -38,7 +38,7 @@ jobs:
     name: runner / alex
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: reviewdog/action-alex@v1
         with:
           github_token: ${{ secrets.github_token }}
diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 48a7213..0ea996a 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -9,7 +9,7 @@ jobs:
     name: runner / black-format (empty)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: ./
         with:
           github_token: ${{ secrets.github_token }}
@@ -29,7 +29,7 @@ jobs:
     name: runner / black-format (github-check)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: ./
         with:
           github_token: ${{ secrets.github_token }}
@@ -72,7 +72,7 @@ jobs:
     name: runner / black-format (github-pr-check)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: ./
         with:
           github_token: ${{ secrets.github_token }}
@@ -85,7 +85,7 @@ jobs:
     name: runner / black-format (github-pr-review)
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac # v4
       - uses: ./
         with:
           github_token: ${{ secrets.github_token }}